How Are Kidney Stones Diagnosed?
The classic presentation of renal colic associated with blood in the urine suggests the diagnosis of kidney stone. Many other conditions can mimic this disease, and the care provider may need to order tests to confirm the diagnosis. In older patients, it is always important to at least consider the diagnosis of a leaking or ruptured abdominal aortic aneurysm (abnormal widening of the large blood vessel that leads from the heart to supply blood to the body) as a source of this type of pain.
Physical examination is often not helpful in patients with kidney stones, aside from the finding of flank (side of the body between the ribs and hips) tenderness. The examination is often done to look for potentially dangerous conditions. The care provider may palpate or feel the abdomen trying to find a pulsatile or throbbing mass that might indicate the presence of an abdominal aortic aneurysm. Listening to the abdomen with a stethoscope may reveal a bruit or rushing noise made by abnormal blood flow through the aneurysm. Tenderness under the right rib cage margin may signal gallbladder disease. Tenderness in the lower quadrants may be associated with appendicitis, diverticulitis, or ovarian disease. Examination of the scrotum may exclude a testicular torsion.
In children, colicky abdominal pain may be associated with intussusception of the intestine.
Symptom control is very important, and medication for pain and nausea may be provided before the confirmation of the diagnosis occurs.
A urinalysis may detect blood in the urine. It is also done to look for evidence of infection, a complication of kidney stone disease. Sometimes, crystals may be seen in the urine and can give a clue as to what type of stone might be present.
Blood tests are usually not indicated, unless the health-care provider has concerns about the diagnosis or is worried about kidney stone complications.
Computerized tomography (CT) scanning of the abdomen without oral or intravenous contrast dye is the most commonly used diagnostic test. The scan will demonstrate the anatomy of the kidneys, ureter, and bladder and can detect a stone, its location, its size, and whether it is causing dilation of the ureter and inflammation of the kidney. The CT can also evaluate many other organs in the abdomen, including the appendix, gallbladder, liver, pancreas, aorta, and bowel. However, since no contrast material is used, there are some limitations to the detail that can be observed in the images of the scan.
Ultrasound is another way of looking for kidney stones and obstruction and may be useful when the radiation risk of a CT scan is unwanted (for example, if a woman is pregnant). Ultrasound requires a specially trained person to obtain and interpret the images. That person might not always be present. Emergency physicians are increasingly being trained to use ultrasound at the bedside. If ultrasound can make the diagnosis, a CT may not necessarily be ordered.
In those patients who already have the diagnosis of a kidney stone, plain abdominal X-rays may be used to track its movement down the ureter toward the bladder. CT scans should be limited to no more than one per year unless absolutely necessary to minimize radiation exposure.